arch/x86: Drop leftover ROMCC support

Remove the last bits of building romstage with romcc.

Change-Id: I70bb1ed23a5aeb87bf7641e0b0bd604a4e622e61
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/26807
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/arch/x86/Kconfig

@@ -107,10 +107,6 @@ config NUM_IPI_STARTS
 	int
 	default 2
 
-config ROMCC
-	bool
-	default n
-
 config CBMEM_TOP_BACKUP
 	def_bool n
 	help